WASHINGTON -- Congress stumbled badly the last time it rewrote military law amid a furor over sexual assaults.

Now, driven by fresh outrage over an Air Force case, some lawmakers seek new changes in the Uniform Code of Military Justice. Their effort is shadowed by lessons that might be learned, or lost, from past Capitol Hill mistakes.

In particular, new legislation prompted by an Air Force general's overturning of a sexual assault conviction reminds some of how Congress once rewrote the military code's sexual assault provisions, called Article 120. One military judge subsequently called the rewrite "almost incomprehensible," another termed it "arguably absurd," and other judges deemed the confusing result unconstitutional.

"The efforts to update Article 120 have certainly vexed military lawyers and judges and provide a useful lesson: Conduct serious public hearings ... hold an open markup and above all don't try to rush," Eugene R. Fidell, who teaches military law at Yale Law School, said in an email interview.

Defense attorney Frank Spinner put it a little more bluntly: "The prior experiences with rewriting Article 120 suggest that Congress is using the military as an experiment in handling sexual assault cases."

Spinner represents Air Force Lt. Col. James Wilkerson, an F-16 pilot who was convicted last year of sexual assault at Aviano Air Base in Italy. In February, Wilkerson was freed from military prison in Charleston, S.C., and restored to active duty after Air Force Lt. Gen. Craig Franklin overturned the conviction.

Franklin's action was authorized by the Uniform Code of Military Justice. But while that power is long-standing, it's rarely exercised.

Air Force officers overturned convictions 40 times in the last five years, out of 3,713 convictions. Five of the overturned cases involved sexual assault. Army officers overturned 68 guilty findings out of 4,603 convictions in the last five years. None involved sexual assault. Marine Corps officers overturned only seven convictions out of 1,768 cases from 2010 to 2012. Data on sexual assault cases wasn't available.

"I want to make sure people understand: One case has to be put in context of a whole system," Sen. Lindsey Graham, R-S.C., an Air Force lawyer, said Wednesday at a hearing of the Personnel Subcommittee of the Senate Armed Services Committee.

Still, the notoriety surrounding the Wilkerson case has spurred multiple legislative proposals, as well as general outrage. The alleged victim, 49-year-old physician assistant Kimberly Hanks, went public and told NBC News she was "absolutely stunned" by Franklin's decision and that he was "protecting one of his own."

A new bill by Sen. Claire McCaskill, D-Mo., would prohibit commanding officers from overturning convictions and would require written explanations if they commuted or lessened sentences. A comparable bill by Rep. Jackie Speier, D-Calif., would prohibit commanding officers from overturning convictions or changing sentences.

"This decision has turned the military on its ear as it relates to the criminal justice system," McCaskill said at the hearing.

Defense Department officials are now evaluating the powers granted to commanding officers, referred to as convening authorities. One important question, among many, will be whether the commanding officers' long-standing clemency powers are still needed in a modern era with full-fledged military appeals courts.

Vice Adm. Nanette DeRenzi, the Navy's judge advocate general, told the Senate panel that it was a good time to reconsider the powers granted commanding officers in light of modern developments, even as she cautioned that lawmakers should be "ever mindful of the second or third order effects" of any potential changes.

Exhibit A: What happened when Congress last adjusted the Uniform Code of Military Justice over sexual assault issues?

Prompted by reports of sexual assaults in Iraq in 2004, Congress directed the Pentagon to review Article 120 sexual assault provisions. The Pentagon task force didn't recommend any statutory changes. Congress, nonetheless, rewrote the law as part of a fiscal 2006 defense bill. The changes, Rep. Loretta Sanchez, D-Calif., said at the time, would be a major step in convicting rapists. Instead, they caused legal chaos.

Under the old military code, prosecutors had to prove that the victim hadn't consented. The rewrite removed that consent provision.

The accused could still claim as a defense that the victim had consented, through a preponderance of evidence. Prosecutors then could defeat this defense if they could show beyond a reasonable doubt that the victim hadn't consented.

This posed several problems. If the defense has enough evidence to show consent, then by definition it's raised a reasonable doubt about what happened. One military appeals court called this conundrum a "legal impossibility." Moreover, though the Constitution puts the burden of proof on the government in a criminal case, the rewrite seemed to shift this burden unfairly to the defense.

"If you had 100 monkeys with a typewriter, they'd probably come up with something like this," Air Force Col. Don Christensen, a trial judge at the time, concluded during a 2009 aggravated sexual assault case.

Citing the rewritten law's serious problems, the U.S. Court of Appeals for the Armed Forces overturned the conviction of former Air Force enlisted man Stephen Prather, who'd been accused of sexually assaulting an intoxicated woman at Travis Air Force Base in California.

Congress quietly rewrote the Article 120 language again in 2011.

"I just think it's a prime example of what happens when legislation is influenced by what they see on 'Oprah' and what advocacy seekers propose, as opposed to what's really necessary," Col. Christensen said of the ill-fated changes during the 2009 trial.

As it happens, Christensen is now the Air Force's chief prosecutor. He handled the Wilkerson prosecution, and he told NBC he considered Hanks "one of the most credible witnesses I've ever dealt with."

"She never changed her story," he told NBC. "It remained 100 percent consistent."